perf: add indexed notification summaries and widget

src/govoplan_notifications/backend/service.py

@@ -6,7 +6,7 @@ from email.message import EmailMessage
 from pathlib import Path
 from typing import Any
 
-from sqlalchemy import event, or_
+from sqlalchemy import and_, case, event, func, or_
 from sqlalchemy.orm import Session
 
 from govoplan_core.core.notifications import NotificationDispatchRequest
@@ -200,21 +200,75 @@ def notification_summary(
     user_id: str | None = None,
     recipient_ids: tuple[str, ...] | None = None,
 ) -> dict[str, int | bool]:
-    base_query = session.query(NotificationMessage).filter(
+    filters = [
         NotificationMessage.tenant_id == tenant_id,
         NotificationMessage.deleted_at.is_(None),
-    )
+    ]
     if recipient_ids is not None:
-        base_query = base_query.filter(NotificationMessage.recipient_id.in_(recipient_ids))
-    active_query = base_query.filter(NotificationMessage.status.notin_(["cancelled", "skipped"]))
+        filters.append(NotificationMessage.recipient_id.in_(recipient_ids))
+    active = NotificationMessage.status.notin_(["cancelled", "skipped"])
+    total, unread, pending, failed = (
+        session.query(
+            func.count(NotificationMessage.id),
+            func.coalesce(
+                func.sum(
+                    case(
+                        (
+                            and_(
+                                active,
+                                NotificationMessage.read_at.is_(None),
+                            ),
+                            1,
+                        ),
+                        else_=0,
+                    )
+                ),
+                0,
+            ),
+            func.coalesce(
+                func.sum(
+                    case(
+                        (
+                            and_(
+                                active,
+                                NotificationMessage.status.in_(
+                                    sorted(PENDING_STATUSES)
+                                ),
+                            ),
+                            1,
+                        ),
+                        else_=0,
+                    )
+                ),
+                0,
+            ),
+            func.coalesce(
+                func.sum(
+                    case(
+                        (
+                            and_(
+                                active,
+                                NotificationMessage.status == "failed",
+                            ),
+                            1,
+                        ),
+                        else_=0,
+                    )
+                ),
+                0,
+            ),
+        )
+        .filter(*filters)
+        .one()
+    )
     show_unread_badge = True
     if user_id:
         show_unread_badge = get_notification_preferences(session, tenant_id=tenant_id, user_id=user_id).show_unread_badge
     return {
-        "total": base_query.count(),
-        "unread": active_query.filter(NotificationMessage.read_at.is_(None)).count(),
-        "pending": active_query.filter(NotificationMessage.status.in_(sorted(PENDING_STATUSES))).count(),
-        "failed": active_query.filter(NotificationMessage.status == "failed").count(),
+        "total": int(total or 0),
+        "unread": int(unread or 0),
+        "pending": int(pending or 0),
+        "failed": int(failed or 0),
         "show_unread_badge": show_unread_badge,
     }